This is Python version 3.1 alpha 1

Python 3.x is a new version of the language, which is incompatible with the
2.x line of releases. The language is mostly the same, but many details,
especially how built-in objects like dictionaries and strings work, have
changed considerably, and a lot of deprecated features have finally been
removed.

This is an ongoing project; the cleanup isn't expected to be complete
until some time in 2008. In particular there are plans to reorganize
the standard library namespace.

Release Schedule

Documentation

All documentation is also available online at the Python web site
(http://docs.python.org/, see below). It is available online for
occasional reference, or can be downloaded in many formats for faster
access. The documentation is downloadable in HTML, PostScript, PDF,
LaTeX (through 2.5), and reStructuredText (2.6+) formats; the LaTeX and
reStructuredText versions are primarily for documentation authors,
translators, and people with special formatting requirements.

This is a work in progress; please help improve it!

The design documents for Python 3 are also online. While the reference
documentation is being updated, the PEPs are often the best source of
information about new features. Start by reading PEP 3000:

For a more detailed change log, read Misc/NEWS (though this file, too,
is incomplete, and also doesn't list anything merged in from the 2.6
release under development).

If you want to install multiple versions of Python see the section below
entitled "Installing multiple versions".

Proposals for enhancement

If you have a proposal to change Python, you may want to send an email to the
comp.lang.python or python-ideas mailing lists for inital feedback. A Python
Enhancement Proposal (PEP) may be submitted if your idea gains ground. All
current PEPs, as well as guidelines for submitting a new PEP, are listed at
http://www.python.org/dev/peps/.

Converting From Python 2.x to 3.x

Python starting with 2.6 will contain features to help locating code that
needs to be changed, such as optional warnings when deprecated features are
used, and backported versions of certain key Python 3.x features.

Testing

To test the interpreter, type "make test" in the top-level directory.
This runs the test set twice (once with no compiled files, once with
the compiled files left by the previous test run). The test set
produces some output. You can generally ignore the messages about
skipped tests due to optional features which can't be imported.
If a message is printed about a failed test or a traceback or core
dump is produced, something is wrong. On some Linux systems (those
that are not yet using glibc 6), test_strftime fails due to a
non-standard implementation of strftime() in the C library. Please
ignore this, or upgrade to glibc version 6.

By default, tests are prevented from overusing resources like disk space and
memory. To enable these tests, run "make testall".

IMPORTANT: If the tests fail and you decide to mail a bug report,
don't include the output of "make test". It is useless. Run the
failing test manually, as follows:

./python Lib/test/regrtest.py -v test_whatever

(substituting the top of the source tree for '.' if you built in a
different directory). This runs the test in verbose mode.

Installing multiple versions

On Unix and Mac systems if you intend to install multiple versions of Python
using the same installation prefix (--prefix argument to the configure
script) you must take care that your primary python executable is not
overwritten by the installation of a different versio. All files and
directories installed using "make altinstall" contain the major and minor
version and can thus live side-by-side. "make install" also creates
${prefix}/bin/python which refers to ${prefix}/bin/pythonX.Y. If you intend
to install multiple versions using the same prefix you must decide which
version (if any) is your "primary" version. Install that version using
"make install". Install all other versions using "make altinstall".

For example, if you want to install Python 2.5, 2.6 and 3.0 with 2.6 being
the primary version, you would execute "make install" in your 2.6 build
directory and "make altinstall" in the others.

Configuration options and variables

A source-to-source translation tool, "2to3", can take care of the
mundane task of converting large amounts of source code. It is not a
complete solution but is complemented by the deprecation warnings in
2.6. This tool is currently available via the Subversion sandbox:

Build Instructions

You can pass many options to the configure script; run "./configure
--help" to find out more. On OSX and Cygwin, the executable is called
python.exe; elsewhere it's just python.

On Mac OS X, if you have configured Python with --enable-framework,
you should use "make frameworkinstall" to do the installation. Note
that this installs the Python executable in a place that is not
normally on your PATH, you may want to set up a symlink in
/usr/local/bin.

On Windows, see PCbuild/readme.txt.

If you wish, you can create a subdirectory and invoke configure from
there. For example:

mkdir debug
cd debug
../configure --with-pydebug
make
make test

(This will fail if you also built at the top-level directory. You
should do a "make clean" at the toplevel first.)